Nonaqueous electrolyte secondary batteries have recently gained wide use as power supplies for driving mobile electronic devices such as smartphones, tablet computers, laptop computers and portable music players. The use of nonaqueous electrolyte secondary batteries also expands to electric tools, power-assisted bicycles, electric vehicles and the like. There has been thus a demand that nonaqueous electrolyte secondary batteries have an increased output.
An electrode plate of a nonaqueous electrolyte secondary battery has an active material layer disposed on a current collector composed of a metal foil, and part of the electrode plate is defined by an exposed portion of the current collector free from the active material layer. A lead is connected to the exposed portion of the current collector so as to establish a current path between the electrode plate and an external terminal. Nonaqueous electrolyte secondary batteries use a nonaqueous electrolyte which has lower ion conductivity than aqueous solutions. To enhance output characteristics, electrode plates used in nonaqueous electrolyte secondary batteries are made thin and long. Thin and long electrode plates make it possible to obtain excellent output characteristics because the current density per unit area of the electrode plate is reduced and the length of the current path in the direction of the thickness of the active material layer is short.
However, an elongated electrode plate has an increased length to the lead in some regions, and consequently the current collection resistance of the electrode plate is increased. To ensure that a thin and long electrode plate will fully exhibit output characteristics, it is necessary to reduce the current collection resistance by optimizing the number of leads and the positions to which the leads are connected. Patent Literature 1 discloses a nonaqueous electrolyte secondary battery in which a plurality of leads are connected to an electrode plate in accordance with the length and width of the electrode plate and the thickness of a current collector. Patent Literatures 2 and 3 disclose nonaqueous electrolyte secondary batteries in which negative electrode leads are connected to both ends of a negative electrode plate in the longitudinal direction.